The disclosure of Japanese Patent Applications No. 2001-303106 filed on Sep. 28, 2001, and No. 2002-027362 filed on Feb. 4, 2002, each including the specification, drawings and abstract, are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates generally to a fluid-filled elastic mount adapted to exhibit a vibration-damping effect on the basis of flows of a fluid filling a fluid chamber thereof, and more particularly to such a fluid-filled elastic mount that is novel in construction and that is suitably usable as an engine mount, a body mount or other mounts for use in automotive vehicles.
2. Description of the Related Art
A suspension-type fluid-filled elastic mount is known as one type of an elastic mount interposed between two members of a vibration system for flexibly connecting these two members in a vibration-damping or isolating fashion. As disclosed in JP-A-63-167142 and JP-A-4-334625, the known suspension-type fluid-filled elastic mount elastically supports a vibrative member, e.g., a power unit of an automotive vehicle, with respect to a subject member whose vibration is to be damped, e.g., a body of the vehicle, by suspending the vibrative member from the subject member. FIG. 24 shows an example of the known suspension-type fluid-filled elastic mount, by way of example, in which a first mounting member 150 attachable to the power unit and a second mounting member 152 attachable to the body are elastically connected with each other by a tapered rubber elastic body 156 disposed between the first mounting member and a lower open-end portion of a vertically extending cylindrical portion 154 of the second mounting member 152 into which the first mounting member 150 is inserted so as to extend into the cylindrical portion 154 for fluid-tightly closing the lower open-end portion of the cylindrical portion 154 of the second mounting member 152. An axially upper end portion of the cylindrical portion 154 of the second mounting member 152 is fluid-tightly closed by a flexible layer 158, whereby a fluid chamber 160 is formed between and defined by the rubber elastic body 156 and the flexible layer 158. A partition member 162 is disposed within the fluid chamber 160 so as to extend in a radial direction perpendicular to an axial direction of the cylindrical portion 154 of the second mounting member 152, and is fixedly supported at its peripheral portion by the second mounting member 152, so that the fluid chamber 160 is fluid-tightly divided by the partition member 162 into two sections, namely, a pressure-receiving chamber 164 partially defined by the rubber elastic body 156 and an equilibrium chamber 166 partially defined by the flexible layer 158. The pressure-receiving chamber 164 and the equilibrium chamber 166 are held in fluid communication with each other through an orifice passage 168.
With such a known suspension-type fluid-filled elastic mount installed in position, a static load or weight of the vibrative member, e.g, the power unit, is applied between the first mounting member 150 and the second mounting member 152 in the axial direction, and a vibrational load is primarily applied between the first and second mounting members 150, 152 in the axial direction, as well. Thus, the known suspension-type fluid-filled elastic mount is tuned to be able to exhibit a damping effect based on resonance or flows of the fluid through the orifice passage 168 exclusively to vibrations applied thereto in the axial direction.
However, the known suspension-type fluid-filled elastic mount may possibly be subjected to vibrations applied thereto in the radial directions perpendicular to the axial direction, depending upon a state of installation thereof. If the suspension-type fluid-filled elastic mount is used as an engine mount for an automotive vehicle, for example, the engine mount may be subjected to vibrational loads applied between the first mounting member 150 and the second mounting member 152 in the radial directions, e.g., in a driving or a longitudinal direction of the vehicle and/or in a transverse direction of the vehicle, when the vehicle is accelerated, runs over steps, goes through corners, or experiences any other possible driving conditions. Actually, the known suspension-type fluid-filled elastic mount has not been sufficiently examined in its damping capability with respect to vibrations applied thereto in the radial directions.
In view of the above, the present inventors have conducted extensive studies and researches on damping characteristics of the known suspension-type fluid-filled elastic mount upon application of vibrations thereto in the radial directions, and it has been revealed that the known suspension-type fluid-filled elastic mount is incapable of exhibiting a desired damping effect with respect to vibrations applied thereto in the radial directions. Especially, the suspension-type elastic mount is prone to experience considerable deterioration of its damping capability at around a higher frequency range of input vibrations corresponding to an acceleration noise range of 300-500 Hz.
It is therefore one object of this invention to provide a suspension-type fluid-filled elastic mount novel in construction and capable of exhibiting an improved damping capability with respect to vibrations applied thereto in a radial direction perpendicular to its axial direction, without deteriorating its damping capability with respect to vibrations applied thereto in the axial direction and its manufacture efficiency due to increase in the number of components or the like.
In an attempt to solve the conventionally experienced problem, the present inventors have been conduced a further extensive study of the suspension-type fluid-filled elastic mount. In the suspension-type fluid-filled elastic mount, the elastic body has a generally frusto-conical shape, and is bonded at its central portion to the first mounting member and at its peripheral portion to the lower open-end portion of the cylindrical portion of the second mounting member, so that the central portion of the elastic body protrudes into an interior space of the cylindrical portion of the second mounting member by a relatively large distance, thereby effectively reducing or preventing occurrence of tensile stress in the elastic body when the elastic mount is installed in position and a static load, e.g., the weight of the power unit acts on the elastic body. When the suspension-type fluid-filled elastic mount constructed as described above is subjected to vibrations applied thereto in radial directions perpendicular to the axial direction, the central portion of the elastic body is forced to be moved back and force or displaced reciprocatively in the radial or diametric directions within the fluid chamber. As a result, an annular region defined by and between the central portion of the elastic body and the cylindrical portion of the second mounting member opposed to the central portion of the elastic body in the radial directions, experiences a volume variation in a circumferential direction thereof, thus causing flows of the fluid in the circumferential direction within the annular region. In view of the above, the present inventors have concluded that the suspension-type fluid-filled elastic mount may suffer from considerable increase in the spring constant based on resonance effect of the fluid flowing through the annular region, upon application of vibrations whose frequency range is higher than a resonance frequency of the fluid flowing through the annular region.
In the light of the above described conclusion, the present inventors have conducted still a further extensive study and research of the suspension-type fluid-filled elastic mount, and then have developed a suspension-type fluid-filled elastic mount according to the present invention. There will be described presently preferred modes of the invention. Each of these modes of the invention is numbered like the appended claims and depending from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to these modes of the invention and combinations of the technical features, but may otherwise be recognized based on the teachings of the present invention disclosed in the entire specification and drawings or that may be recognized by those skilled in the art in the light of the present disclosure in its entirety.
(1) A fluid-filled elastic mount of suspension type, including: (a) a first mounting member; (b) a second mounting member including a cylindrical portion extending in a vertical direction and having a vertically lower open-end portion in which the first mounting member is inserted and disposed; (c) a generally tapered elastic body interposed between the first and second mounting member so as to extend from the vertically lower open-end portion of the cylindrical portion of the second mounting member into an inside of the cylindrical portion for fluid tightly closing the vertically lower open-end portion of the cylindrical portion of the second mounting member and for elastically connecting the first mounting member and the cylindrical portion of the second mounting member with each other; (d) a flexible layer fluid-tightly closing a vertically upper open-end portion of the cylindrical portion of the second mounting member for forming a fluid chamber defined between the generally tapered elastic body and the flexible layer and filled with a non-compressible fluid; (e) a partition member disposed within the fluid chamber so as to extend in a generally radial direction perpendicular to an axial direction of the cylindrical portion, and fixedly supported at a peripheral portion thereof by the second mounting member, for fluid-tightly dividing the fluid chamber into a pressure-receiving chamber partially defined by the generally tapered elastic body and an equilibrium chamber partially defined by the flexible layer; (f) an orifice passage for permitting a fluid communication between the pressure-receiving chamber and the equilibrium chamber; and (g) a restricting projection formed of an elastic body and bonded to the partition member so as to protrude into the pressure-receiving chamber and located in an intermediate portion between the generally tapered elastic body and the cylindrical portion of the second mounting member opposed to the generally tapered elastic body in the generally radial direction, for restricting a generally annular region of the intermediate portion.
In the fluid-filled elastic mount constructed according to this mode of the invention, the restricting projection protruding from the partition member, is disposed in the annular region formed between the radially opposed generally tapered elastic body and cylindrical portion of the second mounting member and extending circumferentially in the pressure-receiving chamber, which annular region is considered to form a fluid passage upon application of a radial vibrational load to the elastic mount, so that a cross sectional area of the fluid passage defined by the annular region is reduced or restricted. This arrangement makes it possible to shift a resonance frequency of the fluid flowing through the annular region to a lower frequency range, which does not matter in terms of a vibration-damping capability of the elastic mount. Therefore, the fluid-filled elastic mount constructed according to this mode of the invention is capable of eliminating or moderating a tendency for its dynamic spring constant to considerably increase at a specific frequency range, e g., an acceleration noise in an automotive vehicle, owing the presence of the restricting projection.
Further, the restricting projection is arranged to be spaced away from both of the generally tapered elastic body and the cylindrical portion of the second mounting member as well as is formed of the elastic body, e.g., a rubber elastic body, permitting a relatively easy elastic deformation of the restricting projection. Therefore, the restricting projection is more likely to be elastically deformed by a pressure of the fluid flowing through the annular region functioning as the fluid passage, resulting in disturbance of flows of the fluid through the annular region. Thus, the present fluid-filled elastic mount of the invention can effectively prevent or reduce a possibility of the considerable increase of its dynamic spring constant upon the application of the radial vibrational load thereto, which is considered due to resonance effect of the fluid flowing through the annular region.
Still further, the restricting projection is formed independently of the generally tapered elastic body and bonded to the partition member so as to protrude into the pressure-receiving chamber according to this mode of the invention, thereby effectively preventing an essential damping characteristic of the elastic mount based on the generally tapered elastic body from being adversely effected or deteriorated by the presence of the restricting projection, while sufficiently maintaining operation efficiency in assembling components of the elastic mount.
(2) A fluid-filled elastic mount according to the above-indicated mode (1), wherein the restricting projection has a tapered shape in cross section with a height dimension larger than a width dimension at a proximal end portion thereof. This arrangement further facilitates elastic deformation of the restricting projection. Thus, the fluid-filled elastic mount is capable of further effectively eliminating or moderating the tendency for its dynamic spring constant to increase when being subjected to vibrations applied thereto in the radial directions, with the help of the elastic deformation of the restricting projection.
Preferably, the restricting projection has an outer circumferential surface extending generally straightly in the axial direction, and has an inner circumferential surface extending generally straightly in the axial direction from the proximal end portion to an intermediate portion thereof while extending in a direction inclined to the axial direction from the intermediate portion to an distal end portion thereof such that the inner circumferential surface gradually extends radially outwardly in an axially outward direction. In this arrangement, the proximal end portion of the restricting projection, which is bonded to the partition member, protrudes downwardly from the partition member by a given height dimension with a generally constant width, and the distal end portion of the restricting projection has a tapered cross sectional shape with an inner surface gradually extending radially outwardly as extending from the intermediate portion to the distal end portion thereof. The restricting projection arranged as described above makes it possible to prevent or restrict an abutting contact of the generally tapered elastic body with the restricting projection, while effectively restricting the annular region defining the fluid passage within the pressure-receiving chamber upon application of vibrations thereto in the radial directions.
(3) A fluid-filled elastic mount according to the above indicated mode (1) or (2), wherein the restricting projection includes a cutout formed in at least one circumferential position thereof. According to this mode of the invention, the spring stiffness of the restricting projection can be made lower owing to the presence of the cutout, thereby allowing the restricting projection to be able to sufficiently restrict the annular region, while facilitating its elastic deformation. Thus, the fluid-filled elastic mount according to this mode of the invention is capable of minimizing a tendency for its dynamic spring constant to considerable increase when being subjected to vibrational loads applied thereto in the radial directions in a yet further effective manner, with the help of the elastic deformation of the restricting projection.
The number and the shape of the cutout are not particularly limited, but may be suitably determined while taking into account its required spring characteristics of the restricting projection. A variety of examples of the cutout include: a circumferentially extending crack-like cutout having a substantially no width; a cutout dividing the restricting projection into at least two parts in the circumferential direction; a cutout extending from the distal end of the restricting projection with a length or depth not to reach the proximal end of the restricting projection; and a substantial cutout formed by partially reducing the wall-thickness of the restricting projection by a sufficient amount.
(4) A fluid-filled elastic mount according to any one of the above-indicated modes (1)-(3), wherein the partition member includes a through hole formed through a central portion thereof and fluid-tightly closed by a movable rubber layer disposed therein such that fluid pressures in the pressure-receiving chamber and the equilibrium chamber act on opposite surfaces of the movable rubber layer, respectively, the movable rubber layer being formed integrally with the restricting projection. According to this mode of the invention, the movable rubber layer is employed for reducing or absorbing the fluid pressure variation in the pressure-receiving chamber so as to prevent the dynamic spring constant from increasing upon application of vibrations over a higher frequency range in which a resistance to flow of the fluid through the orifice passage is too high to permit the flow of the fluid therethrough, and the restricting projection can be formed integrally with the movable rubber layer in an easy and effective manner. Thus, the fluid-filled elastic mount constructed according to this mode of the invention can be manufactured with improved efficiency and with simple structure.
(5) A fluid-filled elastic mount according to any one of the above-indicated modes (1)-(4), wherein the partition member includes a cylindrical stepped portion formed at a radially intermediate portion thereof so as to extend continuously in a circumferential direction thereof, and the restricting projection bonded to an inner circumferential portion of the partition member located radially inward of the cylindrical stepped portion, in a process of vulcanization of a rubber material for forming the restricting projection, and an outer circumferential portion of the partition member located radially outward of the cylindrical stepped portion is fixed by caulking to the upper open-end portion of the cylindrical portion of the second mounting member. According to this arrangement, the inner circumferential portion of the partition member to which the restricting projection is bonded by the vulcanization can be spaced away from the outer circumferential portion of the partition member, which is used for the caulking, with the cylindrical stepped portion interposed therebetween. This makes it possible to effectively prevent, upon the vulcanization of the rubber material for forming the restricting projection within the mold, that the rubber material undesirably extends to the outer circumferential portion of the partition member to be used for the caulking. This arrangement effectively permits the outer circumferential portion of the partition member to be caulked against the cylindrical portion of the second mounting member with strength and durability as well as stability.
(6) A fluid-filled elastic mount according to any one of the above-indicated modes (1)-(5), further comprising at least one first abutting fin integrally formed with at least one of the generally tapered elastic body and the restricting projection such that the at least one first abutting fin is disposed in a space defined between surfaces of the generally tapered elastic body and the restricting projection, which surfaces are opposed to each other in the axial direction, so as to protrude from at least one of the surfaces of the generally tapered elastic body and the restricting projection toward an other one of the surfaces of the generally tapered elastic body and the restricting projection, for restricting or dividing the space at least one circumferential position of the space. In the fluid-filled elastic mount constructed according to this mode of the invention, the cross sectional area of the space defined between the axially or radially opposite surfaces of the generally tapered elastic body and the restricting projection is further reduced by means of the first abutting fin, and accordingly, the cross sectional area of the fluid passage formed in the annular region of the pressure-receiving chamber is more reduced than that in the fluid-filled elastic mount where the restricting projection with no fin is provided. Thus, the fluid-filled elastic mount is capable of further effectively moderating or eliminating the tendency for its dynamic spring constant to increase when being subjected to vibrations over a higher frequency range applied thereto in the radial directions, which may be caused by anti-resonance motion of the non-compressible fluid upon application of the vibrational load over a higher frequency range.
In this respect, the first abutting fin formed on the surface of at least one of the generally tapered elastic body and the restricting projection has a thin-walled fin shape, so that the first abutting fin is more likely to be elastically deformed when being brought into abutting contact with the surface of the other one of the generally tapered elastic body and the restricting projection. Thus, the first abutting fin may exhibit a shock absorbing effect upon the abutting contact between the restricting projection and the generally tapered elastic body, making it possible to eliminate or reduce abutting noises generated upon the above-indicated abutting contact.
The number and the forming portion of the first abutting fin are not particularly limited, provided at least one of the first abutting fin is formed on the surface of the generally tapered elastic body or the surface of the restricting projection, but may be suitably determined while taking into account a required damping capability, efficiency in manufacturing of the elastic mount and the like. For instance, it is preferable to form a pair of first abutting fins formed on the generally tapered elastic body and the restricting projection so as to be opposed to each other in the generally radial direction, thus permitting a further decrease of the cross sectional area of the annular region of the pressure-receiving chamber. Alternatively, a plurality of the first abutting fins are formed on the surface of the generally tapered elastic body and/or the restricting projection so as to be spaced away from each other in the circumferential direction, whereby the fluid-filled elastic mount can improve its damping characteristics with respect to vibrations applied thereto in various radial directions, since the cross sectional area of the fluid passage is reduced by the plurality of the first abutting fins.
(7) A fluid-filled elastic mount according to the above-indicated mode (6), wherein the at least one first abutting fin is held in abutting contact with the other one of the surfaces of the generally tapered elastic body and the restricting projection, in a state where the elastic mount is not installed in position and no external load is applied between the first and second mounting members. According to this mode of the invention, the first abutting fin is held in abutting contact with the generally tapered elastic body or the restricting projection in advance, namely, before the installation of the fluid-filled elastic mount in position. This arrangement assures the first abutting fin to restrict or reduce the cross sectional area of the space defined between the axially or radially opposite surfaces of the generally tapered elastic body and the restricting projection, and the fluid passage formed in the annular region of the pressure-receiving chamber, when the elastic mount is installed on a desired vibration system, e.g., an automotive vehicle, and the axial or radial distance between the generally tapered elastic body and the restricting projection is increased due to the elastic deformation of the generally tapered elastic body caused by a static load acting between the first and the second mounting members. Thus, the fluid-filled elastic mount constructed according to this mode of the invention is capable of effectively moderating considerable increase of its dynamic spring constant that may be caused by resonance of the fluid flowing through the annular region.
In particular, since the first abutting fin is a thin-walled fin-shaped member made of the rubber elastic body, when the first and second mounting members are assembled with each other in the axial direction and the abutting fin is brought into abutting contact with the generally tapered elastic body or the restricting projection, the first abutting fin may exhibit a minimized elastic force in a direction opposite to the axial direction in which the first and second mounting member are assembled with each other, thereby ensuring high operation efficiency in assembling the elastic mount.
(8) A fluid-filled elastic mount according to the above-indicated mode (7), wherein the at least one abutting fin is spaced away from the other one of the surfaces of the generally tapered elastic body and the restricting projection, in a state where the generally tapered elastic body is elastically deformed so as to move the first mounting member vertically downwardly relative to the second mounting member due to a static load applied to the first mounting member in a direction of suspension. This arrangement is effective to avoid the deterioration of the damping capability of the elastic mount due to the presence of the restricting projection. Also, this arrangement further facilitates the elastic deformation of the restricting projection when the elastic mount is installed in position, so that the restring projection is more likely to disturb the flows of the fluid through the annular region. Thus, the fluid-filled elastic mount constructed according to this mode of the invention, is capable of effectively moderating or eliminating the tendency for its dynamic spring constant to considerably increase, which may be caused by resonance of the fluid flowing through the annular region, as a result of the above-described disturbance of the fluid as well as the reduced cross sectional area of the fluid passage by the first abutting fin.
(9) A fluid-filled elastic mount according to any one of the above-indicated modes (1)-(8), further comprising at least one second abutting fin integrally formed with at least one of the generally tapered elastic body and the restricting projection such that the at least one second abutting fin is disposed in a space defined between surfaces of the restricting projection and the generally tapered elastic body and/or the first mounting member, which are opposed to each other in the generally radial direction perpendicular to the axial direction, so as to protrude from at least one of the surfaces toward an other one of the surfaces, for restricting or dividing the space at least one circumferential positions of the space. According to this mode of the invention, the annular region defining the fluid passage is effectively restricted in its cross section, permitting the elastic mount to exhibit the same effects explained above with respect to the elastic mount constructed according to the above-indicated mode (6)-(8) of the invention, in which the first abutting fin is provided. The elastic mount is accordingly capable of effectively moderating or eliminating considerable increase of its dynamic spring constant due to the higher frequency vibrations applied thereto in the radial directions, in a further effective manner. Moreover, the second abutting fin is a thin-walled fin-shaped member made of the rubber elastic body, the second abutting fin may exhibit a shock absorbing effect when being brought into abutting contact with the restricting projection or the generally tapered elastic body upon application of vibrations to the elastic mount in the radial directions, making it possible to eliminate or reduce abutting noises generated upon the above-indicated abutting contact, and to eliminate a possible adverse effects of the second abutting fin on the generally tapered elastic body and the restricting projection. Preferably, the second abutting fin may be employed in combination with the first abutting fin employed in the elastic mount according to any one of the above-indicated modes (6)-(8). In this case, the elastic mount can improve its damping capability with further improved manner.
(10) A fluid-filled elastic mount according to any one of the above-indicated modes (1)-(9), wherein the flexible layer bonded at a peripheral portion thereof to an annular fixing metallic member, and the annular fixing member is superposed at a peripheral portion on a peripheral portion of the partition member and fixed by caulking to the vertically upper open-end portion of the cylindrical portion of the second mounting member together with the partition member. In the fluid-filled elastic mount constructed according to this mode of the invention, the vertically upper open-end portion of the cylindrical portion of the second mounting member can be fluid-tightly closed by the flexible layer, while effectively utilizing a structure for caulking the partition member to the cylindrical portion of the second mounting member.
(11) A fluid-filled elastic mount according to the above-indicated mode (10), wherein the annular fixing metallic member and the partition member cooperate to at least partially define therebetween the orifice passage so as to extend circumferentially at an outer circumferential portion of the partition member. This arrangement makes it possible to easily form the orifice passage with a sufficient length, without sophisticating the structure of the partition member itself. For instance, the partition member may be formed of a single metallic plate, and at least one of the partition member and the annular fixing metallic member is bended so that the partition member and the annular fixing metallic member cooperate to define therebetween a circumferentially extending gap, namely the orifice passage. While the orifice passage is open at one of opposite ends thereof to the pressure-receiving chamber, and at the other end to the equilibrium chamber, the open end of the orifice passage to the pressure-receiving chamber may be formed by a cutout portion formed in the restricting projection, which may provide the cutout of the elastic mount constructed according to the above-indicated mode (3) of the invention.
(12) A fluid-filled elastic mount according to the above-indicated modes (1)-(11), wherein a wall thickness of the generally tapered elastic body varies in a circumferential direction thereof so that the generally tapered elastic body includes a pair of thick-walled portions opposed to each other in a first diametric direction with the first mounting member interposed therebetween and a pair of thin-walled portions opposed to each other in a second diametric direction with the first mounting member interposed therebetween, the first and second diametric directions are orthogonal with each other. According to this mode of the invention, the spring characteristics of the elastic mount on the basis of the generally tapered elastic body, can be softened at a diametric direction in which a pair of thin-walled portions are opposed to each other Thus, the fluid-filled elastic mount is able to exhibit a lower dynamic spring constant in the radial or diametric direction, with the help of the thin-walled portions as well as the effects of the restricting projection.